School of Chemistry and Chemical Engineering, Henan Normal University , Xinxiang, Henan 453007, China.
Acc Chem Res. 2013 Nov 19;46(11):2666-75. doi: 10.1021/ar400099g. Epub 2013 Sep 10.
A dihydrogen bond (DHB) is an electrostatic interaction between a protonic hydrogen and a hydridic hydrogen. Over the past two decades, researchers have made significant progress in the identification and characterization of DHBs and their properties. In comparison with conventional hydrogen bonds (HBs), which have been widely used in catalysis, molecular recognition, crystal engineering, and supramolecular synthesis, chemists have only applied DHBs in very limited ways. Considering that DHBs and conventional HBs have comparable strength, DHBs could be more widely applied in chemistry. Over the past several years, we have explored the impact of DHBs on amine borane chemistry and the syntheses and characterization of amine boranes and ammoniated metal borohydrides for hydrogen storage. Through systematic computational and experimental investigations, we found that DHBs play a dominant role in dictating the reaction pathways (and thus different products) of amine boranes where oppositely charged hydrogens coexist for DHB formation. Through careful experiments, we observed, for the first time, a long-postulated reaction intermediate, ammonia diborane (AaDB), whose behavior is essential to mechanistic understanding of the formation of the diammoniate of diborane (DADB) in the reaction of ammonia (NH3) with tetrahydrofuran borane (THF·BH3). The formation of DADB has puzzled the boron chemistry community for decades. Mechanistic insight enabled us to develop facile syntheses of aminodiborane (ADB), ammonia borane (AB), DADB, and an inorganic butane analog NH3BH2NH2BH3 (DDAB). Our examples, together with those in the literature, reinforce the fact that DHB formation and subsequent molecular hydrogen elimination are a viable approach for creating new covalent bonds and synthesizing new materials. We also review the strong effects of DHBs on the stability of conformers and the hydrogen desorption temperatures of boron-nitrogen compounds. We hope that this Account will encourage further applications of DHBs in molecular recognition, host-guest chemistry, crystal engineering, supramolecular chemistry, molecular self-assembly, chemical kinetics, and the syntheses of new advanced materials.
氢键（DHB）是质子氢和氢化物氢之间的静电相互作用。在过去的二十年中，研究人员在 DHB 的鉴定和特性方面取得了重大进展。与在催化、分子识别、晶体工程和超分子合成中广泛应用的传统氢键（HB）相比，化学家仅以非常有限的方式应用 DHB。考虑到 DHB 和传统 HB 具有相当的强度，DHB 在化学中可能有更广泛的应用。在过去的几年中，我们探索了 DHB 对胺硼烷化学以及胺硼烷和氨化金属硼氢化物储氢合成和表征的影响。通过系统的计算和实验研究，我们发现 DHB 在决定胺硼烷的反应途径（从而决定不同的产物）方面起着主导作用，在这些反应中，相反电荷的氢共存以形成 DHB。通过仔细的实验，我们首次观察到一个长期推测的反应中间体，氨二硼烷（AaDB），其行为对于理解氨（NH3）与四氢呋喃硼烷（THF·BH3）反应生成二硼烷的双氨化物（DADB）的反应机理至关重要。几十年来，DADB 的形成一直困扰着硼化学界。通过对机理的深入了解，我们能够开发出简便的合成方法，用于合成氨基二硼烷（ADB）、氨硼烷（AB）、DADB 和无机丁烷类似物 NH3BH2NH2BH3（DDAB）。我们的例子以及文献中的例子都证明了形成 DHB 并随后消除分子氢是一种可行的方法，可以用于构建新的共价键和合成新材料。我们还综述了 DHB 对硼氮化合物构象稳定性和氢解吸温度的强烈影响。我们希望本综述将鼓励进一步将 DHB 应用于分子识别、主体-客体化学、晶体工程、超分子化学、分子自组装、化学动力学以及新型先进材料的合成。
